The EU will spend up to three months preparing for negotiations before they actually get underway and is adamant that the terms of the divorce must be settled before any future trade arrangements are agreed.

Britain is expected to pay nearly £50 billion in a divorce deal. But even this figure is contested by the British and almost everything is up in the air. The fate of everything from the UK fishing industry to immigration will be decided in negotiations over the next two years.

Here are 11 people at the heart of these talks who will play a defining role in sealing Britain's fate post-Brexit.

Michel Barnier — European Chief Negotiator.

Michel Barnier, Chief Negotiator for the Preparation and Conduct of the Negotiations with the United Kingdom under Article 50 of the Treaty on European Union.
Reuters

Barnier is the EU's most senior Brexit negotiator and will play a crucial role in deciding what the 27-nation bloc is willing to concede in divorce talks. He has warned against Britain walking from negotiations with no deal, saying it is "not what we want." You can read Business Insider's full profile of Barnier here.

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Theresa May — Prime Minister of Britain.

REUTERS/Christopher Furlong/Pool

The weight of a nation rests on May's shoulders. The prime minister is expected to make a success of what will be the most complex negotiations faced by a modern British government — but just what will constitute success is difficult to say at the moment.

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Guy Verhofstadt — European Parliament's top Brexit negotiator and former Belgian prime minister.

Jean-Claude Juncker — President of the European Commission.

Francois Lenoir/Reuters

The European Commission sets EU law, enacting policies set by European Parliament and the European Council. Juncker is the EU's most powerful figure and will play a massive role in deciding what Britain is able to achieve at the negotiating table. He appointed Barnier to his negotiating position.

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Sir Tim Barrow — Permanent Representative of the United Kingdom to the European Union.

Reuters

Barrow is Britain's ambassador to the EU and has spent years working in diplomacy and negotiations. He only recently came to the role, however, following the resignation of Sir Ivan Rogers. Sir Ivan claimed Britain is totally unprepared for Brexit negotiations. Barrow, who delivered the Article 50 letter, is under huge pressure to make a success of Brexit, as May has promised.

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David Davis — Secretary of State for Exiting the European Union.

Gareth Fuller / PA Wire/Press Association Images

David Davis MP heads the Department for Exiting the European Union, making him one of UK government's most important ministers. He was a staunch Brexiteer prior to the referendum and has been central to drafting Britain's Brexit policy. A recent leaked European Commission document suggests EU negotiators are worried about his "street fighter" reputation.

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Philip Hammond — Chancellor of Britain.

Britain's Chancellor of the Exchequer Philip Hammond reads through his Autumn Statement as he poses for a photograph in his office in 11 Downing Street, London, Britain November 22, 2016.
Reuters/Stefan Rousseau

Hammond, also known as "spreadsheet Phil", will be expected to keep Britain's economy in order as he and the rest of government try to negotiate a favourable deal with the EU. The Treasury has set aside over £25 billion to deal with any Brexit related economic shocks, suggesting the Chancellor is preparing for a rough ride.

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Donald Tusk — President of the European Council.

European Council President Donald Tusk holds a news conference at the European Council headquarters after a European Union leaders summit in Brussels, Belgium June 26, 2015.
REUTERS/Eric Vidal

The European Council defines the EU's political policies and strategies, although it does not make law. As such, it is a powerful body within the EU. It was Tusk who opened the Article 50 letter sent to the EU by May on Wednesday. Like Juncker, Verhofstadt, and Barnier, he has a leading role in shaping the EU's negotiating goals.

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Liam Fox — Secretary of State for International Trade and President of the Board of Trade.

WPA Pool /Pool/Getty

Liam Fox MP is tasked with establishing Britain's new role in the world of trade as it prepares to leave its biggest export market. He will spend the next few years travelling around the globe trying to arrange new trade arrangements with other countries. He will likely also be involved in defining Britain's future trading relationship with the EU after Brexit.

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Boris Johnson — Foreign Secretary of Britain.

REUTERS/Djordje Kojadinovic

Boris Johnson MP is the current Foreign Secretary meaning it his the former London mayor's job to maintain positive relations with other countries as Britain tries to make a success of Brexit. Johnson was one of the most prominent "Leave" campaigners in last year's referendum and is seen as one of three key Brexit minister's in May's cabinet, alongside Fox and Davis.

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Angela Merkel — Germany's Chancellor.

Germany and France are the two most politically powerful nations in the EU. However, with France caught up in a Presidential election campaign at the moment, Merkel is left as the most powerful head of state in the EU. Germany has been hugely influential in deciding Union policy in the past, such as in debt negotiations with Greece, and will likely be closely involved in Brexit. Germany also remains a close ally of Britain.